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2020,25(6):575-587, DOI: 10.3878/j.issn.1006-9585.2019.19074
Abstract:Using observed rainfall data from 26 stations in Southwest China for the period 1951–2017, in this study, we investigated the climatic characteristics of rainfall over Southwest China during spring (March–April–May) and each spring month. The rainfall in May was found to account for 55.3% of the total spring rainfall over Southwest China and to have the most significant interannual variations of the spring months. The spring rainfall over Southwest China also shows clear interdecadal variations, which are dominated by the interdecadal variations of the May rainfall. Significant abrupt interdecadal changes (AIDCs) also occur in the spring rainfall, with increased AIDCs having occurred in the middle and the later 1990s after a period of decreased IDACs in the later 1970s. Although the time series of spring rainfall over Southwest China exhibits an insignificant linear trend, the eastern part of Southwest China shows a clear decreasing trend in terms of area, and the western part of Southwest China shows a significant increasing trend. Lastly, the spring rainfall over Southwest China shows significant interannual and interdecadal periodicities, which are also present in the April and May rainfalls. We note that no interdecadal periodicity is evident for March rainfall. In general, the interannual and interdecadal periodicities of spring rainfall are dominated by the variations of May rainfall.
Statistical Characteristics of Wind Field Structures of Tropical Cyclones over the Western North Pacific Based on MTCSWA Data
2020,25(6):588-600, DOI: 10.3878/j.issn.1006-9585.2020.19122
Abstract:On the basis of the MTCSWA (Multiplatform Tropical Cyclone Surface Winds Analysis) data, the climatic statistical characteristics of tropical cyclones (TCs) at different sizes, the variation of the averaged radial extent of different significant wind speed thresholds (i.e., 34, 50, and 65 kt, 1 kt≈0.514 m/s) in different quadrants, and the axisymmetricity of the radial extent of different wind speed thresholds and their correlation with TC intensity over the western North Pacific from 2007 to 2016 are investigated. In this study, the size and intensity of TCs are defined as the azimuthally averaged radius at which wind speed decreases to 34 kt (≈17.5 m/s) from the center and the maximum sustained winds near the TC center, respectively. The mean size of TCs over the western North Pacific Ocean is 221.9 km, with small TCs of 96.4 km and large TCs of 346.4 km. The activity location of large TCs is more concentrated, with a more northward distribution, than that of small TCs. The peak value of the mean size of all TCs occurs in August and October. The mean values of the azimuthally averaged radial extents of the 34, 50, and 65 kt wind speed thresholds are 221.9, 121.0, and 77.4 km, respectively. According to the definition of axisymmetricity, the radial extent of the 34 kt wind speed threshold has the lowest axisymmetricity and the 65 kt wind speed threshold has the highest axisymmetricity. Positive correlations exist between the radial extents of the 34, 50, and 65 kt wind speed thresholds and the TC intensity during the TC’s lifetime, among which the correlation between the radial extent of the 65 kt wind speed threshold and the TC intensity is the lowest. For a certain wind speed threshold, the correlation between its radial extent and TC intensity varies in different quadrants at different stages of the TC’s lifetime. The higher the wind speed is, the weaker the correlation between the axisymmetricity of its radial extent and TC intensity. Only the axisymmetricity of the radial extent of the 34 kt wind speed threshold shows a weak positive correlation with TC intensity during the TC’s lifetime.
2020,25(6):601-615, DOI: 10.3878/j.issn.1006-9585.2020.19154
Abstract:A persistent cold event affected China through late January to early February 2018, causing severe damage to the life and property of the country. The event exhibits a resemblance to the well-known long-lasting snowstorms of January 2008 (“0801” event in brief), because both the events occurred during the La Niña phase along with reduced sea ice in the Arctic during the preceding autumn. In this study, the observational features of the 2018 event and the possible factors for its occurrence are investigated through a comparison with the “0801” event. The 2018 cold event persisted for a relatively shorter period than the “0801” event, with cold air outbreak along with an eastern pathway rather than a northwestern or northern pathway, as was seen in “0801”. Large-scale atmospheric circulation exhibited a substantial difference between the two cases. The Ural blocking and the East Asian grand trough, the two key systems consisting of East Asian winter monsoon (EAWM), which formed a “west-high-east-low” pattern, were significantly stronger in the 2018 event. In comparison, the East Asian grand trough in the “0801” event did not deepen as evidently, despite the similarly enhanced Ural blocking. Instead, a substantially deepened southern branch trough, another important composition of EAWM, developed in “0801” and resulted in a “north-high-south-low” pattern. Also, the Siberian high persisted for a shorter period in the 2018 event. Besides, tropical convection activities exhibited difference between the two cases. Enhanced convection occurred in the Maritime Continent and equatorial western Pacific in the 2018 case, but mainly over the equatorial Indian Ocean during the “0801” event. The latter contributed to the strengthening of the southern branch trough and the western Pacific subtropical high leading to intensified water vapor transportation from the Bay of Bengal and the western Pacific, and intensified precipitation. In comparison, the convection in 2018 was substantially weaker and not so favorable for transporting moisture to South China.
2020,25(6):616-624, DOI: 10.3878/j.issn.1006-9585.2020.19158
Abstract:In order to improve model performance, the impact of the new generation WRF-CMAQ (Weather Research and Forecasting model-Community Multi-scale Air Quality model) air quality model system performance of different resolutions for the main district of Beijing was evaluated in 2018. Based on the data set, with PM2.5 as the primary pollutant, forecast grade accuracy of BJ01 (resolution of 1 km) and BJ03 (resolution of 3 km) domains were found to be better compared to that of the official forecast. More than 50% accuracy rate was achieved with BJ01 and BJ03 domains. Compared with the accuracy rate on the first day of official forecast (59%), accuracy rate using the proposed system reached over 60%. A comprehensive scoring method based on the IAQI (Individual Air Quality Index) accuracy and the grade accuracy is adopted. Results show that BJ03 domain achieved the highest score (75.0 points) followed by BJ01 domain. The official forecast scored 70.6 points while BJ09 (resolution of 9 km) domain achieved the lowest score of 69.1 points. Based on the analysis of the prediction results of 2018 long time series of the model system, the model’s predicted PM2.5 concentration is observed to be consistent with that of the observation trend. In addition, the analysis reveals that the correlation coefficient between the model result of BJ03 domain and that of the observation is 0.76. Good peak value simulation performances are achieved in BJ03 and BJ09 domains where there are large area coverages. Similar error trends in peak value simulation of the three model domains are observed. It is evident that the results from the model with coarse resolution are higher than that of the model with fine resolution, which covers a smaller area. Consistent with the forecast comprehensive score, the statistical analysis results reveal that BJ03 domain prediction has the best performance with an average deviation of 0.83 μg/m3. Compared with the observation forecast, BJ09 domain forecast is generally higher whereas BJ01 domain forecast is observed to be lower. Spatial difference analysis of different resolutions from the same site yields inconsistent results. This study shows that best performance is achieved by BJ01, BJ03, and BJ09 areas for the Nongzhanguan, Wanliu, and Dongsi stations, respectively.
A New Definition of the Western Pacific Subtropical High Indexes Based on Three-Pattern Decomposition of Global Atmospheric Circulation
2020,25(6):625-636, DOI: 10.3878/j.issn.1006-9585.2020.19160
Abstract:Formation and variation dynamics of western Pacific subtropical high (WPSH) have always been an important subject of interest for Chinese meteorologists. However, geopotential height field indexes commonly used in current studies and operational services cannot accurately describe the evolution characteristics of the subtropical high with a global warming background. It is known that the stream function of horizontal circulation defined by the three-pattern decomposition of global atmospheric circulation can equivalently describe the three-dimensional spatial geometric images of the subtropical high. Based on this information, this study proposes the use of the zero contour of the 500 hPa stream function of horizontal circulation as the objective standard to redefine the area, intensity, ridge line, and westward ridge point indexes of the subtropical high. The objectivity and rationality of the newly defined indexes of subtropical high are verified by taking short-term structural evolution characteristics of the subtropical high during summer in 2018 and its relationship with precipitation in eastern China. Results reveal accurate depiction of the large-scale eddy circulation characteristics of the subtropical high with the use of the newly defined indexes of based on the stream function of the horizontal circulation. Additionally, the dynamic and thermodynamic equations concerning the stream function of three-pattern decomposition of global atmospheric circulation provide a new theoretical tool for studying the mechanism of the evolution of the subtropical high anomaly by using the newly defined indexes.
2020,25(6):637-648, DOI: 10.3878/j.issn.1006-9585.2020.20019
Abstract:The characteristics of wind fields and transport pathways in the Guanzhong Basin were revealed based on data from 151 surface meteorological stations in 2017. Wind speed and wind direction data from five representative stations in the basin were analyzed by calculating windy days, daily average wind speed and wind direction frequency in four seasons, and hourly wind field and transport trajectories were calculated by CALMET and trajectory model. The results show that daily average wind speed in the Guanzhong Basin is about 1-3 m s-1, which is higher in summer but lower in autumn and winter. The dominant wind direction in the center of the basin mainly includes northeast and southwest winds along the terrain, while the dominant wind direction around the basin shows a converging trend along the terrain to the center of the basin. Seasonal changes in dominant wind direction at each station are not significant. The wind fields in the basin can be classified into three types, namely, systematic wind field, feeblish systematic wind field, and local atmospheric circulation. The local atmospheric circulation occurs most frequently in the year (74.7%), followed by feeblish systematic wind field (17.3%), and systematic wind field (8%). Airflows of systematic wind field are mainly transported northeasterly, while airflows of feeblish systematic wind field or local atmospheric circulation are transported northeasterly, westerly (including southwesterly), and southeasterly. Trajectories of the local atmospheric circulation are limited to a small area, concentrated between the central basin and southern mountains, which indicates that this wind field is not conducive to air pollution dispersion.
2020,25(6):649-666, DOI: 10.3878/j.issn.1006-9585.2020.20021
Abstract:Model evaluation is an indispensable part of model development. In this study, the authors evaluated the Common Land Model (CoLM) using the latest benchmark software called International Land Model Benchmarking (ILAMB) and compared this model with the Community Land Model version 5 (CLM5) from NCAR. As a land surface model benchmark software, ILAMB can automatically generate graphical diagnostics for model variables and score model performance. Results show that CoLM generally performs well, and its simulation result is close to the benchmark data. Compared with CLM5, CoLM is slightly inferior for gross primary productivity and hydrologic processes. For radiation, CoLM performs as well as CLM5, and is even better for variables such as surface upward long-wave radiation and surface net radiation. Comparing the forcing data of CRUNCEPv7 and GSWP3v1, the authors found differences in the climate average state and observed that the model performance under GSWP3v1 forcing is better. The latent heat flux simulated by CoLM and CLM5 under CRUCNEPv7 forcing has a significant positive bias in the Amazon plains, eastern and southern Asia, and eastern North America, but the bias decreases under GSWP3v1 forcing. The two models overestimate the sensible heat flux in north Africa and central Asia with either of the two forcing datasets. Regarding the radiative process, the surface upward shortwave radiation simulated by CoLM was mainly on the high side in the world, which to a certain extent caused the low level of surface net radiation. The surface upward long-wave radiation scores of four experiments are similar, but a difference exists in the specific spatial distribution.
2020,25(6):667-676, DOI: 10.3878/j.issn.1006-9585.2020.20022
Abstract:A multiscale examination of temperature and precipitation in Mohe from 1958 to 2019 was performed using the Ensemble Empirical Mode Decomposition (EEMD) method and the sliding average t-test method. The results showed that the annual average temperature in Mohe increased by 0.43℃ (10 a)－1 with the mid and late 1980s as the abrupt change points. The daily maximum temperature increased by 0.61℃ (10 a)－1 with the mid and late 1980s as the abrupt change points, while the daily minimum temperature increased by 0.21℃ (10 a)－1 with the early to mid 1980s and late 1990s as the multiple abrupt change points. Furthermore, the rainfall, nighttime rainfall, and daytime rainfall showed a similar change pattern from 1958 to 2019. The trend in the three types of rainfall obtained by EEMD was 14.05 mm (10 a)－1, 7.71 mm (10 a)－1, and 5.12 mm (10 a)－1, respectively. No abrupt change points were detected for all types of precipitation. Both the EEMD and the linear trend analysis found an increase in temperature and precipitation, while the trends obtained by EEMD were greater than that by the linear method, which implies that the traditional linear analysis method underestimates the trends in temperature and precipitation in Mohe.
Correlation of Surface Air Temperature and Precipitation in the Qingjiang River basin and Its Connection with the East Asian Summer Monsoon
2020,25(6):677-694, DOI: 10.3878/j.issn.1006-9585.2020.20035
Abstract:The Precipitation-surface air Temperature Relationship (PTR) constitutes an important indicator of the ecological environment and is closely related to the occurrence of extreme drought/heat wave (or flood/coldness) events. Research has been taking place in several caves of the Qingjiang River basin of the Three Gorges Area. The cave sediments are characterized by long carbon and oxygen isotope sequences which may lead to the construction of a long sequence PTR. Based on modern meteorological observation and reanalysis data, the evolution characteristics and forming reason of the PTR in the Qingjiang River basin can be analyzed, which can provide some physical basis for understanding the relationship between the carbon–oxygen coupling coefficient of the stalagmites and PTR. Based on daily surface air temperature and precipitation observations from six stations, namely Badong (31°2'N, 110°22'E), Jianshi (31°36'N, 109°43'E), Lichuan (30°17'N, 108°56'E), Enshi (30°17'N, 109°28'E), Wufeng (30°12'N, 110°40'E), and Yichang (30°42'N, 111°18'E), and three sets of reanalyses, namely the NCEP Climate Forecast System Reanalysis (CFSR), Japan Meteorological Agency 55-year reanalysis (JRA55), and European Centre for Medium-range Weather Forecasts Interim Reanalysis (ERA-interim), this study investigated the seasonal, interannual, and decadal variability of the PTR and its connection with the East Asian summer monsoon. The following results were obtained: 1) PTR exhibits an obvious seasonality while a significant negative correlation is observed only in summer. 2) Summer PTR exhibits a decadal variability with a periodicity of 20–25 years, close to IPO/PDO. Significant shifts occurred in 1974, 1986, and 1992, with PTR altering from “insignificant” to “significant” and back to “insignificant” again. Specifically, PTR between 1977 and 1992 was significantly negative. 3) There is an overall correspondence between the decadal variability of summer PTR and the strength of the East Asian Summer Monsoon (EASM). When PTR was significantly negative (1977–1992), EASM was weak. However, when PTR was insignificant (1965–1976 and 1993–2011), EASM was strong. 4) Physically, when the summer monsoon weakens, the north and south air flow converges to the south. When the water vapor and ascending motion increases in Qingjiang River basin, it causes an increase in the cloud coverage and precipitation but it reduces the surface heat flux and decreases the surface temperature, leading subsequently to a negative PTR. When the summer monsoon strengthens, the north and south air flow converges to the north, which is not beneficial for the increase of water vapor. On the contrary, it is beneficial for the descending motion. In addition, cloud coverage reduces and temperature increases, resulting in the increase of the adiabatic rate and the positive contribution of precipitation efficiency to precipitation. It is important that, on one hand, the increase of temperature can increase precipitation, and on the other hand, the impact of cloud coverage/precipitation on the temperature weakens but does not disappear. Both conditions make PTR insignificant. 5) The decadal variability of PTR may be linked to the IPO/PDO.
Volume 25,2020 Issue 6
Development of a Meteorology-Chemistry Two-Way Coupled Numerical Model (WRF-NAQPMS) and Its Application in a Severe Autumn Haze Simulation over the Beijing-Tianjin-Hebei Area, China
2014,19(2):153-163, DOI: 10.3878/j.issn.1006-9585.2014.13231
Abstract:An aerosol-optical module based on Mie scattering theory has been implemented in the Nested Air Quality Prediction Modeling System (NAQPMS), and a new coupler has been developed to deal with the interaction between the mesoscale meteorology model WRF (Weather Research and Forecasting Model) and NAQPMS. The one-way off-line and two-way coupled WRF-NAQPMS models are compared to simulate the severe haze in the Beijing-Tianjin-Hebei area from 27 September to 1 October 2013. The results show that the simulated meteorological elements and PM2.5 concentrations from the two-way coupled model with the aerosol direct radiation effect are more consistent with observations. During the haze period, the boundary layer meteorological elements change significantly because of the aerosol direct radiation effect over the Beijing-Tianjin-Hebei area: Incoming solar radiation is reduced by 25%, the 2-m temperature decreases by 1 ℃, the turbulent kinetic energy is reduced by 25%, the 10-m wind speed decreases by up to 0.2 m/s, and the planetary boundary layer (PBL) height is reduced by 25%. These changes make the atmospheric boundary layer more stable and further exacerbate air pollution over the areas where it is already severe, for example, the PM2.5 concentration increases by up to 30% over Shijiazhuang City. The analysis indicates that there is a positive feedback mechanism between haze and boundary layer meteorology, and the two-way coupled model incorporating this feedback is helpful for accurate simulation and forecasting of haze pollution processes.
2008,13(2):123-134, DOI: 10.3878/j.issn.1006-9585.2008.02.02
2010,15(4):337-353, DOI: 10.3878/j.issn.1006-9585.2010.04.01
2011,16(6):733-741, DOI: 10.3878/j.issn.1006-9585.2011.06.07
Abstract:A field performance of Doppler wind lidar Windcube (released by Leosphere Company) was conducted by Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS) and Leosphere Company (from France) at the 325 m meteorological tower site (a part of IAP, located between 3rd North Ring Road and 4th North Ring Road) from 11 December to 14 December 2007. The intercomparison of wind speed and wind direction obtained by Windcube and wind cup anemometers (fixed in the meteorological tower) shows that：1) 10 min averaged wind speed is highly consistent between two types of wind data at six matched levels (63 m, 80 m, 100 m, 120 m, 160 m, and 200 m), the correlation coefficients all equal or exceed 0.98. 2) 10 min averaged wind direction is calculated with the vector method, the correlation coefficients of averaged wind direction at the six levels are 0.99. 3) In comparison with domestic Doppler wind lidar, Windcube performs slightly better in wind speed measuring, and equally well in wind direction measuring. The intercomparison indicates that Windcube is a reliable and swift mobile system mea suring wind profile at low levels.
2004,9(2):278-294, DOI: 10.3878/j.issn.1006-9585.2004.02.05
Variations of the Sea Surface Temperature in the Offshore Area of China and Their Relationship with the East Asian Monsoon under the Global Warming
2011,16(1):94-104, DOI: 10.3878/j.issn.1006-9585.2011.01.09
Abstract:Based on the long time series of mean Sea Surface Temperature (SST) and high-resolution wind field reanalysis data such as HadISST and ERA-40 reanalysis data, the variations of the SST in the offshore area of China and their relationship with the East Asian Monsoon (EAM) in winter (December to the next February) and summer (June to August) are analyzed using the Empirical Orthogonal Function (EOF) and linear regression analysis methods. The results show that: 1) The SST in the offshore area of China in winter or summer exhibited significant interannual and interdecadal variations, and experienced a climate shift in the mid-1980s. The areas with the strongest increase in SST are located in the East China Sea (ECS) in winter and in the Yellow Sea in summer. The SST increased by 1.96°C in winter for the period of 1955-2005 and 1.10 °C in summer for the period of 1971-2006. 2）The EAM has displayed distinct interannual and interdecadal variations with a weakening trend since the end of the 1980s in winter, and since the end of the 1970s in summer. In addition, the linear regression analysis indicates the relationship of the SST to EAM in winter on interdecadal timescale is closer than that on interannual timescale. The interdecadal weakening trend of EAM in winter contributes to the rise in SST in the offshore areas of China, particularly significant in the ECS. Moreover, the related areas of winter or summer mean SST on the interannual timescale in the offshore area of China to the EAM are located in the South China Sea (SCS), and the relationship in winter is much more obvious than that in summer. It is found that the interannual variation of SST in the SCS has obvious relation to the anomalies of the meridional southward and northward winds over the SCS and zonal migration of the subtropical anticyclone over the western Pacific.
2009,14(1):69-76, DOI: 10.3878/j.issn.1006-9585.2009.01.08
Abstract:作为酸雨和细粒子的前体物，SO2对空气质量和人体健康乃至气候与环境的影响十分重要，特别是在不利于扩散的气象条件下，SO2可造成城市短时间严重污染事件。作者以2006年北京325 m气象塔15 m观测平台SO2观测数据为基础，结合同步气象资料分析研究发现：1) SO2浓度冬季高、夏季低；全年日均值为(22.5±22.1)×10-9，最大日均值能达到113×10-9。日变化呈现双峰型，峰值出现在北京时间08:00和22:00；并且季节差异明显，冬季浓度为夏季的4.5倍，采暖期为非采暖期的3.2倍。2) 风向、风速与SO2扩散和输送密切相关，高浓度SO2在东北、东、西方向上出现频率分别为25.8%、13.8%和11.8%；而西北、北方向上的风速越大对SO2清除效果越好。3)利用平均晴空指数划分采暖期阴霾天和晴天，发现阴霾天混合层高度与平均风速仅为(376±204) m和1.1 m·s-1，容易造成SO2累积。4) SO2污染过程呈现周期性的局地累积—清除特征，地形、静风和暖低压是造成北京2006年1月一次重污染事件的成因。
2006,11(1):14-32, DOI: 10.3878/j.issn.1006-9585.2006.01.02
1999,4(1):98-103, DOI: 10.3878/j.issn.1006-9585.1999.01.21
The Mutual Response between Dynamical Core and Physical Parameterizations in Atmospheric General Circulation Models
2011,16(1):15-30, DOI: 10.3878/j.issn.1006-9585.2011.01.02
Abstract:A study of the interaction and mutual response between dynamical core and physical parameterizations by atmospheric general circulation models CAM3.1 and IAP AGCM4.0 is presented. Both the two models were integrated 60 d with ideal physics (Held-Suarez forcing) and with full physical package, respectively. The results show that the mutual responses between dynamical core and physical parameterizations are very different in the troposphere at low latitudes and high latitudes. In the tropical troposphere, the variability of temperature tendency due to dynamical core and that due to physical parameterizations are both large and have significant contributions to the variability of total temperature tendency, and they are in inverse correlation to compensate each other. In the polar middle and upper troposphere, the variability of total temperature tendency mainly relies on the tendency due to dynamical core, while the variation of temperature tendency due to physics is very slow, which can be seen as a stationary forcing. Unlike the tropical regions, there is a positive correlation between the temperature tendency due to dynamics and that due to physics in Polar regions. Moreover, the interactions and mutual responses between the individual physical parameterizations are also analyzed. The results show that the variation of temperature tendency due to moist process is the largest of all the physical parameterizations, and it contributes most to the total temperature tendency due to physics. The variation of temperature tendency due to long wave radiation is also large at high latitudes, while the variation of temperature tendency due to short wave radiation and that due to vertical diffusion are relatively small. There is a negative feedback between the cooling rate of long wave radiation and the heating rate of short wave radiation.
A Comparison of NCEP/NCAR, ERA-40 Reanalysis and Observational Data of Sensible Heat in Northwest China
2009,14(1):9-20, DOI: 10.3878/j.issn.1006-9585.2009.01.02
Variation Characteristics of the Sunshine Duration and Its Relationships with Temperature，Wind Speed，and Precipitation over Recent 59 Years in China
2011,16(3):389-398, DOI: 10.3878/j.issn.1006-9585.2011.03.14
Abstract:Using the data of sunshine duration, temperature, wind speed， and precipitation from 194 basic/reference stations over China from 1951 to 2009, according to the climatic division, the whole domain of China is classified into 11 climatic regions. The authors studied the changes in annual and seasonal trends of the sunshine duration by using linear trend analysis and Morlet wavelet analysis, and analyzed the characteristics between the sunshine duration and the temperature, the wind speed, and the precipitation. It was found that the annual sunshine duration showed a significant decreasing tendency during the recent 59 years with a decreasing rate of 36.9 h·(10 a)-1. The trend variations of the annual sunshine duration in 11 climatic regions were similar with that in the whole nation, only had the difference in degree. The sunshine duration of China changed from intensive to weak in 1981. There is an obvious 7－10-year periodic oscillation for the annual sunshine duration of China before the mid 1990s. The sunshine duration of the four seasons had a bigger decreasing amplitude in the coastal areas than in the inland areas, and in the South than in the North. There was a negative correlation between the annual sunshine duration and the temperature (correlation coefficient is -0.52), but a positive correlation between the annual sunshine duration and the wind speed (correlation coefficient is 0.76), and a negative correlation between the annual sunshine duration and the precipitation (correlation coefficient is -0.27). The first two correlation coefficients and the last correlation coefficient passed 99.9% and 95% confidence levels，respectively.
Simulation of Potential Vegetation Distribution and Estimation of Carbon Flux in China from 1981 to 1998 with LPJ Dynamic Global Vegetation Model
Abstract:The LPJ DGVM (Lund Potsdam Jena Dynamic Global Vegetation Model), which is a process based model, is used to simulate the vegetation distribution and estimate the interannual variation of net primary production (NPP), heterotrophic respiration (Rh) and net ecosystem production (NEP)in China from 1981 to 1998. It is shown that there are six main plant functional types (PFTs) besides the desert,that is tropical broadleaved evergreen tree, temperate broadleaved evergreen tree, temperate broadleaved summergreen tree, boreal needleleaved evergreen tree, boreal needleleaved summergreen tree and C3 perennial grass. In China, the total NPP varies between 2.91 Gt·a-1(C) (1982) and 3.37 Gt·a-1(C) (1990), increases by 0.025 Gt (C) average per year and has an increasing trend of 0.96%. The total Rh varies between 2.59 Gt·a-1(C) (1986) and 319 Gt·a-1(C)(1998), grows by 1.05% per year and by 0.025 Gt(C) per year. The linear trend of NPP and Rh for C3 perennial grass is more remarkable than those for other PFTs. The simulation of NEP is reasonable when the fire is brought in the model. Annual total NEP varies between -0.06 Gt·a-1(C)(1998)and 0.34 Gt·a-1(C)(1992). It is demonstrated that the terrestrial ecosystem is carbon sink in China. The above results are similar to those simulated by other models.
Cause and Anomalous Characteristics of the South China Sea Monsoon Trough Producing Heavy Rainfall in South China
2011,16(1):1-14, DOI: 10.3878/j.issn.1006-9585.2011.01.01
Abstract:Atmospheric processes associated with the South China Sea (SCS) monsoon trough which caused the heavy rainfall in pentad 3 of August 2007 in South China are analyzed using the reanalysis data of NCEP and satellite images. The results indicate that the Asian summer monsoon trough has independent space structure, convergence in the low layers and divergence in the high layers are in the south of the Asian summer monsoon trough. The climate analysis shows that both the Indian monsoon trough and the SCS monsoon trough reach their maximum in 〖JP2〗August. The SCS monsoon trough in pentad 3 of August 2007 was located in South China coastal areas and had strong intensity. The convergence in the low layers and divergence in the high layers were also stronger. The Indian monsoon trough was also stronger. The strengthened South Asian high locating over the Tibetan Plateau is the main cause for the strengthening of the Asian monsoon trough. The subtropical high in the western Pacific is located over Japan and is intensified, which is propitous to the northward 〖JP〗movement and the enhancing of the SCS monsoon and monsoon trough. The increased temperature over the Tibetan Plateau induces the stronger easterly in the upper levels, westerly in the low levels,and the enhancing convergence in the low layers and divergence in the high layers of the SCS monsoon trough. The long wave trough in the westerly belt is intensified and extends to Southwest China, which causes the SCS monsoon trough to become stronger. The SCS monsoon trough has an intraseasonal period. The intraseasonal oscillation has an important effect on the northward movement and enhancement of the SCS summer monsoon trough.
2008,13(1):75-83, DOI: 10.3878/j.issn.1006-9585.2008.01.10
2011,16(1):47-59, DOI: 10.3878/j.issn.1006-9585.2011.01.05
Abstract:Based on the MODIS observations, the performance of Interactive Canopy Model(ICM), a dynamic vegetation model including the carbon and nitrogen cycles of the terrestrial ecosystem, has been assessed. The Leaf Area Index (LAI), a key parameter with seasonal variation in vegetation dynamics, is simulated by ICM and compared with the MODIS data. The results show that ICM can simulate the main characteristics of the seasonal LAI fluctuations. Compared to the observation, LAI is overestimated in high and low latitudes, but underestimated in middle latitudes by the model. The underestimation of the LAI in middle latitudes is followed by the vegetation sprout for the reason that the modeled growth is always slower than the observed one. The bimodal distributions for the tropical evergreen broadleaf trees and crops have not been well captured. In addition, the simulated results for the grassland are more reasonable than other Plant Function Types (PFTs). The results will provide important clues for the parameterization improvement and parameters optimization of the ICM.
2002,7(2):209-219, DOI: 10.3878/j.issn.1006-9585.2002.02.08
Combination of Wavelet Decomposition and Least Square Support Vector Machine to Forcast Atmospheric Ozone Content Time Series
2010,15(3):295-302, DOI: 10.3878/j.issn.1006-9585.2010.03.09
Abstract:The atmosphere ozone content forecast model was established based on the combination of wavelet decomposition and advanced Least Square Support Vector Machine (LSSVM) regression. This can be approached in three steps: (1)The observations were decomposed into several different frequency signal subsets,(2)the independent prediction models of decomposed signals with Takens delay embedding theorem and Least-Squares Support Vector Machine (LSSVM) were set up, (3)independent predicted results were integrated as the final prediction with wavelet reconstruction. Application experiments with data from Xianghe and the other three observation stations show that the method can make better prediction effectively for the atmospheric ozone content, as compared with conventional Support Vector Machine(SVM) and Artificial Neural Network(ANN).
2010,15(5):541-550, DOI: 10.3878/j.issn.1006-9585.2010.05.02
Abstract:The Nested Air Quality Prediction Modeling System (NAQPMS) has been applied to the routine air quality forecast in Beijing during the Olympic Games. Monte Carlo method is used to analyze the uncertainty of ozone simulation of NAQPMS during the Olympic Games, from 8 to 24 Aug 2008. Latin hypercube sampling has been used for multi-variables sampling, and 50 ensemble runs have been made with 154 parameter uncertainties being considered together. By the temporal average, the most important parameter to the surface ozone output uncertainty in Beijing is the local precursor emissions during the day time. Other important factors include NO2 photolysis coefficient, wind direction, precursor emissions from the surrounding areas of Beijing, and vertical diffusion coefficient. The wind direction and precursor emissions from the surrounding areas of Beijing have the greatest impact on the uncertainty of daytime ozone simulation at higher levels (above about 150 m). The main uncertainty factors in ozone simulation at night are local NOx emissions and vertical diffusion coefficient. Given the predefined input uncertainties, the average uncertainty of ozone simulation is 19 ppb, ranging from 2 ppb to 49 ppb.
A Research on the Application of Spatial Difference Method in Quality Control of Surface Meteorological Data
2010,15(3):229-236, DOI: 10.3878/j.issn.1006-9585.2010.03.02
Abstract:A new Quality Control（QC）technique called spatial difference method is introduced in detail and applied to spatial checking of some basic meteorological elements at seven representative stations in China for the year of 2007 in order to evaluate the applicability of this approach．The checking tests are conducted on ten basic meteorological elements including daily mean pressure，maximum pressure，minimum pressure，mean temperature，maximum temperature，minimum temperature，mean vapor pressure，mean surface temperature, maximum surface temperature, and minimum surface temperature．It is shown that this method works well in identifying errors of single meteorological element．As compared with spatial regression test on discriminating artificial errors，the spatial difference method is more effective．Furthermore，same as the other spatial checking methods，the distribution of neighboring weather stations should be concerned necessarily as influence factors．
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Editor in chief: 李崇银